Many studies have been made to utilize carbon nanotubes as conductors of micro-electronic elements, electrodes such as FPDs, microstructures and high-strength material adsorbents.
This carbon nanotube comprises a graphite sheet having a cylindrically rounded form and may be classified into a single-wall carbon nanotube with a single sheet and a multi-wall carbon nanotube with plural sheets overlapped telescopically on each other. Many of generally well known single-wall carbon nanotubes have a diameter of 1 to 2 nm and a length of several μm. As to many multi-wall carbon nanotubes, the diameter of the outermost layer is several tens nm, the diameter of the innermost layer is several μm to 10 nm and the length is several μm.
Meanwhile, in recent years, a multi-wall carbon nanotube has been discovered in which although the diameter of the outermost layer is likewise about 10 nm, layers are densely formed up to the center and the diameter of the finest layer at the innermost side is about 0.4 nm. Such a diameter as small as about 0.4 nm in the innermost carbon nanotube is not only the finest among those which have been discovered so far but also a size equal to the molecular diameter of C20 which is the smallest fullerene and is such a fineness limit that a carbon nanotube smaller than this does not exist stably. Namely, this is a multi-wall carbon nanotube densely fitted to the limit where no more tube is generated in the inside.
The characteristics of this densest multi-wall carbon nanotube are that it is chemically stable like usual multi-wall carbon nanotubes and, in addition, it is considered that this densely fitted carbon nanotube is more improved in mechanical strength. Also, it has been clarified that the innermost carbon nanotube having a diameter of 0.4 nm has metallic qualities.
As a method of manufacturing a densest multi-wall carbon nanotube such as those aforementioned, a method in which a carbon nanotube is produced by arc discharge using a carbon electrode in a hydrogen atmosphere has been already reported. However, this method has the drawback that the amount of the multi-wall carbon nanotube is very small and the resulting carbon nanotube has many impurities.
The invention of the patent application of this case has been made in the situation as aforementioned and it is an object of the invention to solve the prior art problem and to provide a method of manufacturing a densest multi-wall carbon nanotube with high purity highly efficiently.